May 2007 marked the centenary of the birth of pioneering environmentalist, Rachel Carson (1907-1964). Publication of “Silent Spring” in 1962 marked a change in public opinion towards the use of chemicals and the natural environment.

During the Second World War, to protect troops, the insecticide DDT was sprayed widely by the American army in malarial areas such as southern Italy. After the war, it became a popular means of controlling insect pests – older readers will remember DDT powder for the garden and for woodworm. Sprayed over large areas, however, it destroyed insect life indiscriminately, and led, notoriously, to the thinning of bird eggshells. In “Silent Spring” Carson evoked a dawn with no bird song. Despite fierce opposition from the chemical industry, her meticulous research and dogged persistence won public support and this highly influential book has become a classic.

Carson introduced the idea of the “chain of events”. In the 1950s, American elms were sprayed to protect them from Dutch elm disease. After one season, migratory robins were found to be dying in some numbers. Leaf litter from the trees had been consumed by earthworms, which in turn were eaten by the birds. In this country, DDT in sheep dip affected peregrines and golden eagles.

Use of DDT is now banned, but a complete ban, particularly in Africa, is controversial. As yet, there is no alternative that is either as cheap or as effective at controlling malaria.

There are really interesting comments on how effective she was an educationalist and campaigner, but I found the most moving part of this programme was a reading from part of the first chapter of “Silent Spring”

On Page 120 of Silent Spring: Rachel Carson explains the lack of young birds by saying: “… [The reproductive capacity of the birds has been so lowered by some environmental agent that there are now almost no annual additions of young to maintain the race. Exactly this sort of situation has been produced artificially in other birds by various experimenters, notably Dr. James DeWitt of the U.S. Fish and Wildlife Service. Dr. DeWitt’s now classic experiments on the effects of a series of insecticides on quail and pheasants have established the fact that exposure to DDT or related chemicals, even when doing no observable harm to the parent birds, may seriously affect reproduction. … For example, quail into whose diet DDT was introduced throughout the breeding season survived and even produced normal numbers of fertile eggs. But few of the eggs hatched”[emphasis added].

Carson gives no indication of how many might be considered as “few eggs hatching.” Perhaps she thought that her readers would never see the rather obscure journal in which DeWitt’s results were published in 1956, the Journal of Agriculture and Food Chemistry. Otherwise, she surely would not have so badly misrepresented DeWitt’s results! The dosage he fed the quail was 100 parts per million in all their food every day, which was roughly 3,000 times the daily DDT intake of humans during the years of the greatest DDT use!

The quail did not just hatch “a few” of their eggs, as DeWitt’s data clearly reveal (Table 3). As the published data from DeWitt’s experiments show, the “controls” (those quail with no DDT) hatched 83.9 percent of their eggs, while the DDT-fed quail hatched 75 to 80 percent of theirs. I would not call an 80 percent hatch “few,” especially when the controls hatched only 83.9 percent of their eggs.

Carson either did not read DeWitt’s article, or she deliberately lied about the results of DeWitt’s experiments on pheasants, which were published on the same page. The “controls” hatched only 57.4 percent of their eggs, while the DDT-fed pheasants, (dosed with 50 ppm of DDT in all of their food during the entire year) hatched 80.6 percent of theirs. After two weeks, the DDT chicks had 100 percent survival, while the control chicks only had 94.8 percent survival, and after 8 weeks the DDT chicks had 93.3 percent survival while the control chicks only had 89.7 percent survival. It was false reporting such as this that caused so many leading scientists in the United States to take Rachel Carson to task.*